chapter 10 muscular tissue

Copyright © John Wiley and Sons, Inc. All rights reserved.

Chapter 10

Muscular

Tissue

Lecture slides prepared by Curtis DeFriez, Weber State University


Excitation-Contraction CouplingWe will come back to the term excitation-

contraction coupling in a little bit

Before we can describe the

entire process, from

thinking of moving a

muscle to actual contraction

of sarcomeres, we must

first explore the processes

that occur at the ___________ junction


___________-___________ coupling (___ coupling) involves events at the junction between a motor neuron and a skeletal muscle fiber

Neuromuscular Junction


An enlarged view of the neuromuscular junctionThe presynaptic membrane is on the neuron while the postsynaptic membrane is the ___________plate on the muscle cell. The two membranes are separated by a space, or “cleft”



Conscious thought (to move a muscle) results in

activation of a motor neuron, and release of the

neurotransmitter ___________ (AcCh) at the NM

junction

The enzyme

_________________

breaks down AcCh

after a short period

of time



The plasma membrane on the “far side” of the NMJ

belongs to the muscle cell and is called the ___________

The motor end plate is rich in chemical (___________) -

gated sodium channels that respond to AcCh. Another

way to say this: The receptors for AcCh are on the

ligand-gated ______ channels on the motor end plate



The ___________ events at the NMJ transmit the electrical events of a neuronal action potential into the ___________ events of a muscle action potential



Neuromuscular JunctionInteractions Animation

Neuromuscular Junctions

You must be connected to the internet to run this animation.


The muscle __ is propagated over the surface of

the muscle cell membrane (___________) via

voltage (___________)-gated Na+ and K+ channels

Muscle Action Potential


By placing a micropipette inside a muscle cell,

and then measuring the electrical potential

across the cell membrane, the phases of an

_________________

(AP) can be

graphed (as in this

figure)



The behavior of the _____

and ___ channels, at various

points in the AP, are seen

in this graphic

Na+ gates open during the

___________ phase

K+ gates open during the

___________ phase



Generating An Action PotentialThe flow of ions through cell a membrane looks a lot

like a "piece" of electricity flowing through a wire

(but not as fast)

Generating an AP on the muscle membrane involves

the transfer of information from an ___________signal

(down the neuron), to a ___________signal (at the NMJ),

back to an ___________ signal (depolarization of the

sarcolemma)

This added complexity (changing from electrical to

chemical back to electrical signals) provides

necessary control of the process


Excitation-Contraction Coupling



EC coupling involves putting it all together

The thought process going on in the brain

The AP arriving at the neuromuscular junction

The regeneration of an AP on the muscle

membrane

Release of Ca2+ from the sarcoplasmic reticulum

Sliding of thick on thin filaments in sarcomeres

Generation of muscle tension (work)


The brain

The motor neuron

Acetylcholine (ACh)

Acetylcholinesterase

enzyme

Ach receptors on the

motor endplate

Na+-K+ channels on the

sarcolemma

Na+ flow

K+ flow

Regenerate AP

The T-tubules

The SR

Ca2+ release

Troponin/

Tropomyosin

ATP

Myosin binding

Filaments slide

Muscles contract

Role Players in E-C coupling



Contraction of SarcomereInteractions Animation

Contraction of a Sarcomere



Sources of Muscle EnergyStored ______

3 seconds

Energy transferred from stored

______________________

12 seconds

___________production

___________ glucose use

30-40 seconds


Sources of Muscle Energy


In a state of ___________, muscle use of O2

and nutrients is balanced by the production of

manageable levels of waste products like

_______

_______ - 70-80% of the energy used by

muscles is lost as heat - muscle activity is

important for maintaining body temperature

___________(anaerobic)

Skeletal Muscle Metabolism


___________, or "Excess Post-Exercise Oxygen

Consumption" (EPOC) is the amount of

___________ required after exercise in skeletal

muscle to:

___________ ATP stores

___________ creatine phosphate and

myoglobin stores

___________ lactic acid back into pyruvate

so it can be used in the Krebs cycle to replenish

ATP



Muscle Metabolism

Muscle Metabolism



Cardiac and Smooth Muscle Metabolism

In response to a single AP, cardiac muscle

contracts ____ times longer than skeletal muscle,

and must continue to do so, without ______, for

the _____ of the individual

To meet this constant demand, cardiac muscle

generally uses the rich supply of O2 delivered by

the extensive coronary circulation to generate

ATP through ___________ respiration


Cardiac and Smooth Muscle Metabolism

Like cardiac muscle, smooth muscle (in your

deep organs) is ___________ and is not under

voluntary control (your heart beats and your

stomach digests without you thinking about it).

Unlike cardiac (and skeletal muscle) however,

smooth muscle has a low capacity for

generating ATP and does so only through

___________ (___________)


___________ Unit is composed of a ___________

plus all of the muscle cells it innervates

_______ precision

• Fewer muscle fibers per neuron

• Laryngeal and extraocular muscles (2-20)

_______ precision

• Many muscle fibers per neuron

• Thigh muscles (2,000-3,000)

The Motor Unit


Activities requiring extreme precision (like the subtle

and rapid movements of the eye) involve muscles

with ___________ motor units (1-4 muscle

fibers/neuron)

The Motor Unit


___________ principle of muscle contraction

When an individual muscle fiber is stimulated to

depolarization, and an action potential is

propagated along its sarcolemma, it must

contract to it’s full force—it can’t ___________

contract

Also, when a single motor unit is recruited to

contract, all the muscle fibers in that motor unit

must all contract at the same time

The Motor Unit


Skeletal muscle fibers are not all alike in appearance

or function. By appearance:

_____ muscle fibers (the dark meat in chicken legs)

have a high myoglobin content, more mitochondria,

more energy stores, and a greater blood supply

_______ muscle fibers (the white meat in chicken

breasts) have less myoglobin, mitochondria, and

blood supply

Skeletal Muscle Fiber Types


Slow ___________ fibers (SO) are small, appear dark red, are

the least powerful type. They are very fatigue resistant

Used for endurance like running a marathon

Fast ______________________ fibers (FOG) are intermediate in

size, appear dark red, and are moderately resistant to fatigue.

Used for walking

Fast ___________ fibers (FG) are large, white, and powerful

Suited to intense anaerobic activity of short duration



Most skeletal muscles are a mixture of all three types

of skeletal muscle fibers; about half the fibers in a

typical skeletal muscle are slow oxidative (SO) fibers

Within a particular motor unit all the skeletal

muscle fibers are the _______ type

The different motor units in a muscle are

___________ in a specific order depending on the

task being performed (fast anaerobic activity for

maximal force, etc.)



There is a brief delay called the ___________as the

AP sweeps over the sarcolemma and Ca2+ ions are

released from the sarcoplasmic reticulum (SR)

During the next phase the fiber is actively

___________

This is followed by ___________as the Ca2+ ions are

re-sequestered into the SR and myosin binding

sites are covered by tropomyosin

Temporary loss of excitability is call the

___________– All muscle fibers in a motor unit will

not respond to a stimulus during this short time

Tension in a Muscle


A ___________ is recorded when a stimulus that results

in contraction (force) of a single muscle fiber is

measured over a very brief millisecond time frame

Tension in a Muscle


Applying increased numbers of action potentials to a muscle fiber (or a ___________, a muscle, or a muscle group) results in fusion of contractions (___________) and the performance of useful work

Tension in a Muscle


Two motor units, one in green, the other in purple, demonstrate the concept of progressive activation of a muscle known as ___________Recruitment allows a muscle to accomplish increasing gradations of contractile strength

Tension in a Muscle


Muscle TensionInteractions Animation

Control of Muscle Tension



Muscle Contraction___________ contractions results in

___________Concentric isotonic is a type of muscle

contraction in which the muscle shorten while

generating force

Eccentric isotonic is a contraction in which

muscle tension is less than the resistance (the

muscle lengthens)

___________ contractions results in ___________

Muscle force and resistance are equal

Supporting objects in a fixed position and

posture


Muscle Contraction


Exercise-induced muscle damage

After intense exercise electron micrographs

reveal considerable muscle damage including

torn sarcolemmas and disrupted Z-discs

Blood levels of proteins normally confined

only to muscle (including myoglobin and the

enzyme creatine kinase) increase as they are

released from damaged muscle

Imbalances of Homeostasis


___________

A sudden involuntary contraction of a single

muscle within a large group of muscles – usually

painless

___________

Involuntary and often painful muscle contractions

Caused by inadequate blood flow to muscles (such

as in dehydration), overuse and injury, and

abnormal blood electrolyte levels



Disease States and Disorders

___________ (myofibrosis)

Replacement of muscle fibers by excessive

amounts of connective tissues (fibrous scar

tissue)

___________

Hardening of the muscle caused by calcification

Both myosclerosis and muscle fibrosis occur as a

result of trauma and various metabolic disorders



Aging

In part due to decreased levels of physical activity,

with aging humans undergo a _____, ___________ loss of

skeletal muscle mass that is replaced largely by fibrous

connective tissue and adipose tissue

Muscle strength at 85 is about _____ that at age 25

Compared to the other two fiber types, the relative

number of slow oxidative fibers appears to ___________


chapter 10 muscular tissue

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